ES2743478T3 - Polyolefin photovoltaic backsheet comprising a stabilized polypropylene layer - Google Patents

Abstract

A polyolefin PV backsheet comprising a layer of polypropylene stabilized with (A) at least one amine hindered with 2,2,6,6-tetraalkylpiperdine or 2,2,6,6-tetraalkylppierazinone, alone or in combination with a moiety of triazine, (B) a thioester, and further comprising (C) at least one hindered hydroxybenzoate and / or (D) an ortho hydroxy triazine compound.

Description

DESCRIPTION

Polyolefin photovoltaic backsheet comprising a stabilized polypropylene layer

Field of the Invention

This invention relates to photovoltaic (PV) modules or cells. In one aspect, the invention relates to back sheets of PV modules, while in another aspect the invention relates to back sheets of PV module comprising polypropylene. In a further aspect, the invention relates to PV module back sheets comprising polypropylene and a package of additives to stabilize the back sheet against UV / visible light degradation and thermal aging, while conferring resistance to flame without the use of flame retardant additives.

Background of the invention

US Patent documents 7,759,417, 6,051,164, 6,867,250 and 6,843,939 show the protection of polyolefins against degradation by UV / visible light, heat and oxidation, through the use of various (1) hindered amine light stabilizers (HALs) , from the English "hindered amine light stabilizers") such as ortho-tris-aryl triazine light absorbers, hindered hydroxyl benzoates, nickel extinguishers (eg, nickel phenolate), etc., and (2) antioxidants such as hindered phenol, hindered arylalkyl phosphite, and trisaryl phosphite. However, these references do not show that HALS and / or antioxidants confer flame resistance to a polyolefin.

The combination of a thioester (a secondary antioxidant) with a hindered phenol (a primary antioxidant) can synergistically provide long-term thermal stabilization (Gachter / Muller, Plastics Additives Handbook, Hanser Publishers, 1993). However, the thioester used in the presence of HALS can also reduce the effectiveness of HALS due to its interaction with the degradation by-products of the thioester. This results in poor natural wear properties in polyolefin (Polymeric Materials Encyclopedia: P, Vol. 8, 1996, p. 5994, and J. Sedlar, J. Marchal, J. Petruj, Polymer Photochemistry Vol. 2, Number 3 , May 1982, pages 175-207, p. 200). The application of stabilizer combinations in solar cell backsheets is shown in WO 2014/205802, US 2011/100438 and WO 2013/003541.

Some flame retardants (FR), such as halogenated FRs, which are typically used to achieve effective low flame propagation, also usually have a negative effect on the UV stability provided by HALS (Robert L Gray, Robert E. Lee and Brent M. Sanders, Journal of Vinyl and Additive Technology, Vol. 2, Number 1, pages 63-68, March 1996). Some hindered amines, eg, N-alkoxy or NOR HALS, can enhance UV stability in the presence of FR due to lower basicity of NOR HALS and a reduction of the negative impact of FR on HALS. However, usually both FR and NOR HALS are necessary to achieve flame retardation (see, for example, US Patent 5,393,812). Useful inorganic FRs typically require very high loads (up to 60 percent by weight (% w / w)) of the composition to be effective, and can negatively affect the mechanical properties or processing characteristics of the composition and / or of an article made with the composition.

Some hampered halogenated amines provide flame retardance efficiency and UV stability to thin fibers and films of polyolefin fibers (see EP 1462 481 or US 2012/0108709). They can be combined with UV absorbers or other non-interaction HALS to further improve the UV stability of the final article. However, these additives are known to cause a discoloration of polypropylene (Aubert M., et al, Polymer Degradation and Stability, 96 (2011) 328-333) and there is no evidence of good long-term thermal aging (LTHA, English "long term heat aging") which is critical for the certification of PV modules. Similarly, BASF describes other organic-based FR agents such as AZO or AZONOR (described, for example, in US 2010/0144935) but these also do not provide a good LTHA or good UV stabilization.

An organic-based FR comprising additives of acids, salts and phosphine esters (see, for example, US Patents 8,097,753, 7,485,745 and US 2007/0213563) can achieve a good flame retardation , but this also does not provide UV or LTHA stabilization. Other non-halogenated flame retardant agents may provide some flame retardation and UV stability, but they confer a high degree of yellowish color (recorded according to the yellowing index) and do not provide significant LTHA stabilization.

There is a need to provide PV modules with long-term UV stability, long-term thermal aging and flame resistance without the use of FR additives. Specifically, there is a need for a low cost PV backsheet or at least one layer of a backsheet PV, which exhibits (1) low flame spread of <100, determined by ASTM E162-02a, (2 ) Long-term thermal aging greater than 105 ° C measured according to the Relative Thermal Index (RTI) and evaluated using a UL 746B standard and reflected through the retention of tensile strength measured by ASTM D882 after aging at high temperatures (e.g., 150 ° C), and (3) superior UV stability (>) 1000 hours reflected through a retention of> 70% of tensile strength properties and good color retention (eg, YI less than (<) 5) in Xenon Arc exposure (IEC 61730, ASTM D2565, ASTM G151, ASTM G155) or alternatively in QUV exposure (ASTM G154). This combination of LTHA, UV and FR properties is necessary for certification by the "International Electrotechnical Commission" (IEC) and "Underwriters Laboratories" (UL) on polyolefin PV backsheet films used to construct PV modules.

Summary of the invention

In one embodiment the invention is a polyolefin PV backsheet comprising a polypropylene layer stabilized with (A) at least one amine hindered with 2,2,6,6-tetralalkylpiperidine or 2,2,6,6-tetraalkylpiperazinone, a or both in combination with a functional triazine moiety, (B) a thioester, and, (C) at least one hindered hydroxybenzoate, and / or (D) an ortho hydroxyl triazine compound. Examples of triazine functional moieties include those described in US Pat. 6,843,939, preferably oligomeric (i), (ii) polymeric, or (iii) triazines having a weight average molecular weight (Mw) of at least 500. This stabilized polypropylene layer exhibits a low rate of flame spread of <100 without the use of FR agents, and good conditions of resistance to environmental factors, while providing the long-term thermal aging benefits necessary for a satisfactory PV module as described above.

In one embodiment the invention is a multilayer PV backsheet which, in addition to comprising a stabilized polypropylene layer as indicated above, also comprises (I) at least one additional layer comprising a polypropylene other than polypropylene stabilized with (A) at minus one hindered amine with 2,2,6,6-tetraalkylpiperidine or 2,2,6,6-tetraalkylpiperazinone, one or both in combination with a functional triazine moiety, (B) at least one hindered hydroxybenzoate, and optionally, ( C) an ortho hydroxyl triazine compound, and (II) at least one layer of polypropylene stabilized with (A) at least one amine hindered with 2,2,6,6-tetraalkylpiperidine or 2,2,6,6-tetraalkylpiperazinone, one or both in combination with a functional triazine moiety, (B) a thioester, and, (C) at least one hindered hydroxybenzoate and / or (D) an ortho hydroxyl triazine compound.

In another embodiment, an integrated backsheet can be used to manufacture a PV module, wherein said integrated backsheet comprises a back encapsulating tie layer attached to a backsheet or attached to one or more layers of a backsheet, wherein said backsheet comprises a stabilized polypropylene layer as described above. The anterior posterior encapsulating layer preferably comprises a polyolefin.

Optionally, one of the layers of the PV backsheet described in subsequent embodiments may comprise at least one of (1) a non-halogenated inorganic or organic compound, (2) a halogenated non-phosphorous organic compound, (3) a halogenated phosphorous compound , or (4) an anti-drip agent. These PV backsheets exhibit a low rate of fire propagation of <100, and good resistance properties to environmental conditions, while providing the long-term thermal aging performance required for a successful PV module.

In one embodiment, the polypropylene layer further comprises at least one of an acid scavenger, metal deactivator, primary antioxidant (such as hindered phenol), and a secondary antioxidant (such as hindered arylalkyl phosphate or trisaryl phosphite).

In one embodiment, the polyolefin PV backsheet comprises a 3-layer structure in which the two outer or outer layers are joined by an intermediate or tie-down layer. At least one of the two outer layers is a stabilized polypropylene layer as described above.

In one embodiment, the integrated polyolefin PV backsheet comprises a multilayer structure in which an outer layer comprising polypropylene is bonded to an encapsulating layer comprising a polyolefin, optionally using a tie down layer.

In one embodiment, the polyolefin PV backsheet or the integrated polyolefin PV backsheet are manufactured using a co-extrusion method or a lamination method. Examples of methods include, but are not limited to, thermal lamination, extrusion lamination and adhesive lamination. Preferred methods are co extrusion and extrusion lamination.

In one embodiment, the invention is a PV module comprising a polyolefin backsheet as described in any of the previous embodiments.

Brief description of the figures

Figure 1 is a schematic of a PV module.

Detailed description of the invention

Definitions

Unless otherwise indicated, implicit in the context, or customary in the art, all parts and percentages are based on weight and all test methods are current as of the date of presentation of this description. For the purposes of patent practice in the United States, the content of any patent, patent application or patent publication referenced, is incorporated in its entirety by reference (or its US version equivalent is thus incorporated by way of reference), especially in relation to the description of the definitions (provided they are not inconsistent with any definitions specifically provided in this description) and the general knowledge of the technique.

The numerical ranges of this description are approximate, and therefore may include values outside the range unless otherwise indicated. The numerical ranges include all values between the lower and upper values, including these, in increments of one unit, provided there is a separation of at least two units between any lower value and any higher value. As an example, if a compositional, physical or other property, such as, for example, molecular weight, viscosity, melt index, etc., is between 100 and 1,000, it is intended that all individual values , such as 100, 101, 102, etc., and sub-ranges, such as 100 to 144, 155 to 170, 197 to 200, etc., are expressly listed. For ranges that contain values that are less than one or that contain fractional numbers greater than one (e.g., 1.1, 1.5, etc.), a unit is considered to be 0.0001, 0.001, 0, 01 or 0.1, as appropriate. For ranges that contain individual digital numbers less than ten (eg, 1 to 5), a unit of 0.1 is typically considered. These are just examples of what is specifically intended, and all possible combinations of numerical values between the lowest value and the highest value cited should be considered expressly mentioned in this description. The numerical ranges are provided in this description for, among other things, the amount of organo clay of the PV backsheet and / or the encapsulant.

"Photovoltaic cells", "PV cells" and similar terms mean a structure containing one or more photovoltaic materials of any of several inorganic or organic types that are known in the art and from the teachings of prior art photovoltaic modules . For example, commonly used photovoltaic materials that include, but are not limited to, crystalline silicon, polycrystalline silicon, amorphous silicon, (di) selenium copper gallium indium (CIGS), copper selenide indium (CIS), cadmium telluride, Gallium arsenide, dye-sensitized materials, and organic solar cell materials. As shown in Figure 1, PV cells are typically employed in a laminated structure and have at least one light reactive surface that converts the incident light into electrical current. Photovoltaic cells are well known to specialists in this field and are generally packaged within photovoltaic modules that protect the cell (s) and allow their use in their various application environments, typically in outdoor applications. The PV cells can be flexible or rigid in nature and include the photovoltaic materials and any protective coating surface that are applied in their production, as well as the appropriate wiring and electronic circuits.

"Photovoltaic modules", "PV modules" and similar terms mean a structure that includes a PV cell. In one embodiment, the PV module 10 is represented by the example structure shown in Figure 1, and contains at least one photovoltaic cell 11 (in this case with a single light-reactive or effective surface directed or oriented upwards in the direction of the top of the page) surrounded or encapsulated in a light-transmitting protective encapsulant sub-component 12a on the top or on the front surface and a protective encapsulant sub-component 12b on the back or rear surface, which optionally It is light transmitter. Combined, 12a and 12b form an encapsulating component 12, shown here as a combination of two encapsulating layers that form a "sandwich" with the cell. The light transmitting cover sheet 13 has an inner surface in adherent contact with a front facial surface of the encapsulating film layer 12a, layer 12a which in turn is disposed on a PV cell 11 and in adherent contact with it. The film of the backsheet 14 (which can be single-layer or, as shown here, multi-layer) acts as a substrate and supports a back surface of the PV cell 11 and the optional encapsulating film layer 12b, which, in in this case, it is arranged on a rear surface of the PV cell 11. The backsheet layer 14 (and even the encapsulating sub-layer 12b) need not be light transmitters if the surface of the PV cell with respect to which it is opposite is not effective, that is, reactive to sunlight.In the case of a flexible PV module, as the description "flexible" implies, it would comprise a flexible thin film photovoltaic cell 11.

"Composition" and similar terms mean a mixture of two or more materials, such as a polymer that is mixed with other polymers or that contains additives, fillers, or the like. Compositions include pre-reaction, reaction and post-reaction mixtures, the latter of which will include reaction products and by-products, as well as unreacted components of the reaction mixture and decomposition products, if the there would be, formed from one or more components of the pre-reaction or reaction mixture.

"Mixture", "polymer blend" and similar terms mean a composition of two or more polymers. Said mixture may be miscible or not. Said mixture may be separate phase or not. Said mixture may or may not contain one or more domain configurations, as determined by electronic transmission spectroscopy, light scattering, X-ray scattering, and any other method known in the art. The mixtures are not laminated, but one or more layers of a laminate may contain a mixture.

"Polymer" means a compound prepared by polymerizing monomers, both of the same type and of different types. The generic term polymer thus encompasses the term homopolymer, usually used to refer to polymers prepared from a single type of monomer, and the term interpolymer as defined below. It also covers all forms of interpolymers, e.g., random, block, etc. The terms "ethylene / a-olefin polymer" and "propylene / a-olefin polymer" are indicative of interpolymers as described below. It should be noted that, although a polymer is often referred to as "constituted by" monomers, "based on" a Specified monomer or a specified type of monomer, "containing" a specified monomer content, or the like, is obviously understood to refer to the polymerized remnant of the specified monomer and not to unpolymerized species.

"Interpolymer" means a polymer prepared by polymerization of at least two different monomers. This generic term includes copolymers, commonly used to refer to polymers prepared from two or more different monomers, and includes polymers prepared from more than two different monomers, eg, terpolymers, tetrapolymers, etc.

"Polyolefin", "polyolefin polymer", "polyolefin resin" and similar terms mean a polymer produced from a single olefin (also called alkene, with the general formula C ⁿ H ²ⁿ ) as a monomer. Polyethylene is produced by polymerizing ethylene with or without one or more comonomers, polypropylene polymerizing propylene with or without one or more comonomers, etc. Thus, the polyolefins include interpolymers such as ethylene / a-olefin copolymers, propylene / a-olefin copolymers, etc.

"(Met)" indicates that the methyl substituted compound is included in the term. For example, the term "ethylene glycidyl (meth) acrylate" includes ethylene glycidyl acrylate (E-GA) and ethylene glycidyl methacrylate (E-GMA), individually or collectively.

The "melting point" as used herein is typically measured by the differential scanning calorimetry (DSC) technique to measure melting peaks of polyolefins as described in US Pat. 5,783,638. Many mixtures comprising two or more polyolefins will have more than one melting peak; Many individual polyolefins will comprise only one melting peak.

PV module

The invention is described in the context of a PV module as illustrated in Figure 1, it being understood that the construction of the PV module and the construction materials can vary widely, e.g., the backsheet can be monolayer or multilayer, Polymers of the encapsulant and backsheet constructions may vary, the materials and construction of the PV cell may vary, etc. A fundamental element of the invention is the ability of the organo clay to capture impurities in the polymers that, if not captured, can lead to current leakage and loss resulting from the efficiency of the PV cell. This is particularly true with PV module components made of polymers containing catalyst residue that can subsequently migrate, typically in an ionic form, throughout the structure.

Layer C of the backsheet

In one embodiment, the polyolefin resins useful in the lower layer or Layer C of the backsheet have a melting point of at least 125 ° C, preferably greater than 14 ° C, more preferably greater than 150 ° C and even more preferably higher than 160 ° C. Said polyolefin resins are preferably polymers based on propylene, usually referred to as polypropylenes. Said polyolefins are preferably prepared with multi-site catalysts, eg, Zeigler-Natta and Phillips catalysts. In general, polyolefin resins with a melting point of at least 125 ° C often exhibit desirable stiffness properties useful in protecting the electronic device of the module.

With respect to polyolefin resins in general, such as those suitable for Layer C or for other polymeric components of the present invention, the single monomer (or the primary monomer in the case of interpolymers) is typically selected from ethylene, propene (propylene ), 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene and preferably is propylene for the resin of Layer C polyolefin. If the polyolefin resin is an interpolymer, then the different comonomer (s) of the first or primary monomer is / are typically one or more a-olefins. For the purposes of this invention, ethylene is an a-olefin if the primary monomer is propylene or a higher olefin. The co-a-olefin is then preferably a different linear, branched or cyclic C ^2-20 a-olefin. Examples of C ^{2-20 a} -olefins for use as comonomers include ethylene, propene (propylene), 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1 dodecene, 1 -tetradecene, 1-hexadecene and 1-octadecene. The a-olefins for use as comonomers may also contain a cyclic structure such as cyclohexane or cyclopentane, resulting in an a-olefin such as 3-cyclohexyl-1-propene (allyl cyclohexane) and vinyl cyclohexane. Although they are not a-olefins in the classical sense of the term, for the purposes of this invention certain cyclic olefins, such as norbornene and related olefins, are a-olefins and can be used as a comonomer instead of part or all of the a-olefins described above. Similarly, styrene and its related olefins (eg, a-methylstyrene, etc.) are aolefins for the purposes of the comonomers according to this invention. Acrylic and methacrylic acid and their respective ionomers, and acrylates and methacrylates, are also comonomer a-olefins for the purposes of this invention. Illustrative polyolefin copolymers include, but are not limited to, ethylene / propylene, ethylene / butene, ethylene / 1-hexene, ethylene / 1-octene, ethylene / styrene, ethylene / acrylic acid (EAA), ethylene / methacrylic acid (EMA) , ethylene / acrylate or methacrylate, EVA and the like. Illustrative terpolymers include ethylene / propylene / 1-octene, ethylene / propylene / butene, ethylene / butene / 1-octene, and ethylene / butene / styrene. The copolymers can be random or block.

The high melting polyolefin resins (having a melting point of at least 125 ° C), which are useful in the present invention and preferred for use as all or most of the C layer at the bottom of the sheet Subsequent multilayer of Figure 1 include propylene-based polymers, also referred to as propylene polymers or polypropylenes, which include, for example, polypropylene or propylene copolymers comprising a majority of units derived from propylene and a minority of units derived from another. a-olefin (including ethylene). These propylene-based polymers include polypropylene homopolymer, propylene copolymers and one or more additional olefin monomers, a mixture of two or more homopolymers or two or more copolymers, and a mixture of one or more homopolymers with one or more copolymers, provided having a melting point of 125 ° C or more. Polypropylene-based polymers can vary widely in form and include, for example, substantially isotactic propylene homopolymer, random propylene copolymers, and graft or block propylene copolymers.

The propylene copolymers preferably comprise at least 85, more preferably at least 87 and even more preferably at least 90, mole percent units derived from propylene. The rest of the propylene copolymer units are derived from units of at least one α-olefin having up to about 20, preferably up to 12 and more preferably up to 8, carbon atoms. The α-olefin is preferably a linear, branched or cyclic C3-20 aolefin, as described above.

In general, preferred propylene polymer resins include polypropylene homopolymers, preferably high crystallinity polypropylene such as high rigidity and hardness polypropylenes. Preferably the MFR of the propylene polymer (measured as dg / min at 230 ° C / 2, 16 kg) is at least about 0.5, preferably at least about 1.5, and more preferably at least about 2.5 dg / min and less than or equal to about 25, preferably less than or equal to about 20, and most preferably less than or equal to about 18 dg / min.

In general, preferred propylene polymer resins for Layer C have heat fusion values (reflecting the relatively higher crystallinity) measured by DSC of at least about 60 Joules per gram (J / g), more preferably at least about 90 J / g, even more preferably at least about 110 J / g and most preferably at least about 120 J / g. For the measurements of the heat of fusion, as it is known in a general way and carried out by specialists in the field, the DSC equipment is used as described in general below with a nitrogen atmosphere at 10 ° C / min from 23 ° C to 220 ° C, isothermally maintained at 220 ° C for 3 minutes, lowered to 23 ° C at 10 ° C / min and raised again to 220 ° C at 10 ° C / min. The second heat data is used to calculate the heat of fusion of the melting transition.

The following are illustrative, but not limited to, propylene polymers that can be used in the backsheets of this invention: a propylene impact copolymer that includes, but is not limited to, DOW Polypropylene T702-12N; a propylene homopolymer that includes, but is not limited to, DOW Polypropylene H502-25RZ; and a random propylene copolymer that includes, but is not limited to, DOW Polypropylene R751-12N. Other polypropylenes include some of the VERSIFY ™ polymers available from The Dow Chemical Company, VISTAMAXX ™ polymers available from ExxonMobil Chemical Company, and PRO-FAX ™ polymers available from Lyondell Basell Industries, eg, PRO-FAX ™ SR- 256M, which is a clarified propylene copolymer resin with a density of 0.90 g / cm3 and an MFR of 2 g / 10 min, PRO-FAX ™ 8623, which is an impact propylene copolymer resin with a density of 0.90 g / cm3 and an MFR of 1.5 g / 10 min. Other propylene resins include CATALLOY ™ polypropylene (homo- or copolymer) in-reactor mixtures with one or more propylene-ethylene or ethylene-propylene copolymer (all available from Basell, Elkton, MD), the homopolymer of Shell propylene KF 6100; the propylene copolymer of Solvay KS 4005; and the Solvay KS 300 propylene terpolymer. Additionally, INSPIRE ™ D114, which is a branched impact copolymer polypropylene with a melt flow rate (MFR) of 0.5 dg / min (230 ° C / 2.16 kg) and a melting point of 164 ° C would be a suitable polypropylene. In general, a suitable high crystallinity polypropylene with high rigidity and hardness includes, but is not limited to, INSPIRE ™ 404 with an MFR of 3 dg / min, and INSPIRE ™ D118.01 with a melt flow rate of 8.0 dg / min (230 ° C / 2.16 kg), (both also available from The Dow Chemical Company).

Propylene polymer blending resins can also be used when polypropylene resins such as those described above can be mixed or diluted with one or more additional polymers, including polyolefins such as those described below, to the extent that the other polymer is ( i) miscible or compatible with polypropylene, (ii) has little, or no, negative impact on the desirable properties of polypropylene, e.g., hardness and modulus, and (iii) polypropylene constitutes at least about 55, preferably at less about 60, more preferably at least about 65 and even more preferably at least about 70, percent by weight of the mixture. The polypropylene polymer can also be mixed with cyclic olefin copolymers such as the TOPAS ™ 6013F-04 cyclic olefin copolymer available from Topas Advanced Polymers, Inc. with preferred amounts when at least about 2, preferably 4, and more preferably 8 are used. weight percent, and even 40, preferably 35 and more preferably 30 weight percent. In general, the propylene polymer resins for Layer C may comprise an impact modifier such as ethylene octene plastomers such as AFFINITY ™ p L 1880G, e G 8100G, and PL 1850G available from The Dow Chemical Company. In general, these are used in amounts of at least about 2 percent by weight, preferably at least about 5 and more preferably at least about 8 percent by weight, and preferably less than about 45% by weight, preferably less than about 35 percent by weight and more preferably less than about 30 percent by weight. Other candidate mixing or impact modification resins are ethylene / propylene gums (optionally mixed with in-reactor polypropylene) and one or more block composite materials such as those described herein. Combinations of impact modifiers of different types can also be used.

Other additives that could be used with propylene polymer resins are inorganic fillers such as talc (which includes talc coated with epoxy), colorants, flame retardants (halogenated and non-halogenated) and synergistic flame retardant compounds such as Sb2O3.

Layer B of the backsheet

The composition of Layer B of the backsheet of an embodiment of the invention, often referred to as a "tie down" layer, is selected to adhere, preferably by co-extrusion or alternatively, but less preferably, by a lamination process ( such as extrusion lamination, thermal lamination or adhesive lamination) to layers C and A (or optionally another layer). Layer B typically comprises a resin of crystalline block copolymer composite material ("CBC") and / or certain resins of block copolymer composite material ("BC's"), CBC's and BC's collectively referred to as "composite resin resins of block and crystalline block ”,“ composite resins ”or“ (C) BC's ”. Layer B may alternatively comprise a mixture of one or more CBC and with one or more BC, or a mixture of one or both of said resins with one or more additional resins.

The term "block copolymer" or "segmented copolymer" refers to a polymer comprising two or more chemically distinct regions or segments (referred to as "blocks"), joined in a linear fashion, that is, a polymer comprising chemically units differentiated that are joined (covalently linked) end to end with respect to polymerized functionality, rather than in a pendant or grafted manner. In a preferred embodiment, the blocks differ in the amount or type of comonomer incorporated therein, the density, the amount of crystallinity, the type of crystallinity (e.g., polyethylene vs. polypropylene), the attributable crystal size to a polymer of said composition, the type or degree of tacticity (isotactic or syndiotactic), regioregularity or regio-irregularity, the amount of branching, which includes long chain branching or hyperbranching, homogeneity, or any other chemical or physical property. The block copolymers of the invention are characterized by unique distributions of the polydispersity of the polymer (PDI or Mw / Mn) and the block length distribution, due, in a preferred embodiment, to the effect of carrier agent (s). in combination with the catalyst (s).

As used herein, the terms "block composite material" or "block copolymer composite material" are different from resins of "crystalline block composite materials" or "crystalline block copolymer composite material" based on the amount of comonomer polymerized with the ethylene polymer and the ethylene block of the composite. The term "BC" generally refers to polymers comprising (i) a soft ethylene (EP) copolymer having polymerized units in which the comonomer content is greater than 10% mol and less than 90% mol of ethylene polymerized, and preferably greater than 20% mol and less than 80% mol, and most preferably greater than 33% mol and less than 75% mol, (ii) a crystalline α-olefin polymer (CAOP), in which the α-olefin monomer is present in an amount greater than 90 and up to 100 molar percent, and preferably greater than 93 molar percent, and more preferably greater than 95 molar percent, and most preferably greater than 98 molar percent , and (iii) a block copolymer, preferably a diblock, having a soft segment and a hard segment, wherein the hard segment of the block copolymer has essentially the same composition as the olefin-a polymer of the block composite material and the segm The soft block copolymer has essentially the same composition as the soft ethylene copolymer of the block composite. Block copolymers can be linear or branched. More specifically, when produced in a continuous process, block composites desirably possess a PDI of between 1.7 and 15, preferably between 1.8 and 3.5, more preferably between 1.8 and 2.2 , and most preferably between 1.8 and 2.1. When produced in a discontinuous or semi-continuous process, the block desirably comprises a PDI between 1.0 and 2.9, preferably between 1.3 and 2.5, more preferably between 1.4 and 2.0, and most preferably between 1.4 and 1.8. Such block composite materials are described, for example, in US Patent Application Publications. No. US2011-0082257, US2011-0082258 and US2011-0082249, all published on April 7, 2011, and incorporated herein in reference to the descriptions of the block composite materials, the processes for manufacturing them and the methods to analyze them.

As mentioned above, alternatively or additionally to the CBC (discussed in more detail below), certain suitable "BC" resins may be employed in Layer B of the films according to the present invention. Specific suitable "BC's" comprise a soft ethylene copolymer (EP) having a comonomer content greater than 80% mol and up to 90% mol and preferably greater than 85% mol and most preferably greater than 87% mol, but otherwise, a BC such as the one described herein in general.

The term "crystalline block composite material" (CBC) (which includes the term "crystalline block copolymer composite material") refers to polymers comprising a crystalline ethylene-based polymer (CEP), an alpha-olefin-based polymer crystalline (CAOP), and a block copolymer having a block of crystalline ethylene (CEB) and a block of crystalline alpha-olefin (CAOB), wherein the CEB of the block copolymer has essentially the same composition as the CEP of the material block compound and the CAOB of the block copolymer has essentially the same composition as the CAOP of the block composite. Additionally, the compositional division between the amount of CEP and CAOP will be essentially the same as between the corresponding blocks of the block copolymer. Block copolymers can be linear or branched. More specifically, each of the respective segments may contain long chain branches, but the block copolymer segment is substantially linear, the opposite of containing grafted or branched blocks. When produced in a continuous process, crystalline block composites desirably possess a PDI between 1.7 and 15, preferably between 1.8 and 10, preferably between 1.8 and 5, more preferably between 1.8 and 3.5. Such crystalline block composite materials are described, for example, in the following patent applications filed: PCT / US11 / 41189; US 13/165054; PCT / US11 / 41191; US 13/165073; PCT / US11 / 41194; and US 13/165096; All submitted on June 21, 2011.

CAOB refers to highly crystalline blocks of polymerized alpha olefin units in which the monomer is present in an amount greater than 90 mol%, preferably greater than 93 mole percent, more preferably greater than 95 mole percent, and preferably greater than 96 percent molar. In other words, the comonomer content of the CAOBs is less than 10 mole percent, and preferably less than 7 mole percent, and more preferably less than 5 mole percent, and most preferably less than 4 mole percent. The CAOBs with propylene crystallinity have corresponding melting points of 80 ° C and above, preferably 100 ° C and above, more preferably 115 ° C and above, and most preferably 120 ° C and above. In some embodiments, the CAOB comprises all or substantially all propylene units. CEB, on the other hand, refers to blocks of polymerized ethylene units in which the comonomer content is 10% mol or less, preferably between 0% mol and 10% mol, more preferably between 0% mol and 7% mol and most preferably between 0% mol and 5% mol. Said CEB has corresponding melting points that are preferably 75 ° C and above, more preferably 90 ° C, and 100 ° C and above.

"Hard" segments refers to highly crystalline blocks of polymerized units in which the monomer is present in an amount greater than 90 mole percent, and preferably greater than 93 mole percent, and more preferably greater than 95 mole percent, and most preferably greater than 98 mole percent. In other words, the comonomer content in the hard segments is more preferably less than 2 molar percent, and more preferably less than 5 molar percent, and preferably less than 7 molar percent, and less than 10 molar percent . In some embodiments, the hard segments comprise all or substantially all propylene units. The "soft" segments, on the other hand, refer to amorphous, substantially amorphous or elastomeric blocks of polymerized units in which the comonomer content is greater than 10% mol and less than 90% mol and preferably greater than 20% mol e less than 80% mol, and most preferably greater than 33% mol and less than 75% mol.

The BC's and / or CBC's are preferably prepared by a process comprising contacting an addition polymerizable monomer, or a mixture of monomers, under addition polymerization conditions with a composition comprising at least one addition polymerization catalyst, a co-catalyst and a chain carrier agent, said process being characterized by the formation of at least part of the growing polymer chains under differentiated process conditions in two or more reactors operating under steady-state polymerization conditions or in two or more zones of a reactor that operates in conditions of polymerization of piston flow. In a preferred embodiment, the BC's and / or CBC's comprise a block copolymer fraction that has a more likely distribution of block lengths.

Suitable processes useful for producing block composite materials and crystalline block composite materials can be found, for example, in US 2008/0269412.

Suitable catalysts and catalyst precursors suitable for use in the preparation of the BC's and / or CBC's of the invention include metal complexes such as those described in WO2005 / 090426, in particular, those described starting on page 20, line 30 to page 53, line 20, which are incorporated herein by reference. Suitable catalysts are also described in US 2006/0199930; US 2007/0167578; US 2008/0311812; US 7,355,089 B2; or WO 2009/012215, which are incorporated herein by reference in relation to the catalysts.

Preferably, the BC's and / or CBC's comprise propylene, 1-butene or 4-methyl-1-pentene and one or more comonomers. Preferably, the block polymers of the BC's and the CBC's comprise in polymerized form propylene and ethylene and / or one or more C ^4-20 α-olefin comonomers, and / or one or more additional copolymerizable comonomers, or comprise 4-methyl -1-pentene and ethylene and / or one or more C ^{4-20 a} -olefin comonomers, or comprise 1-butene and ethylene, propylene and / or one or more C ⁵ -C ²⁰ a-olefin comonomers and / or one or more additional copolymerizable comonomers. Suitable additional comonomers are selected from diolefins, cyclic olefins and cyclic diolefins, halogenated vinyl compounds, and aromatic vinylidene compounds.

The comonomer content in the resulting BC's and / or CBC's can be measured using any suitable technique, with techniques based on nuclear magnetic resonance spectroscopy (NMR) being preferred. It is highly desirable that part or all of the polymer blocks comprise amorphous or relatively amorphous polymers such as propylene, 1-butene or 4-methyl-1-pentene copolymers and a comonomer, especially random propylene, 1-butene or 4-methyl copolymers -1-pentene with ethylene, and any remaining polymer blocks (hard segments), if any, predominantly comprise propylene, 1-butene or 4-methyl-1-pentene in polymerized form. Preferably said segments are highly crystalline or stereo-specific polypropylene, polybutene or poly-4-methyl-1-pentene, especially isotactic homopolymers.

Additionally preferably, the block copolymers of the BC's and / or CBC's comprise between 10 and 90 percent by weight of crystalline or relatively hard segments and between 90 and 10 percent by weight of amorphous or relatively amorphous segments (soft segments) , preferably between 20 and 80 percent by weight of crystalline or relatively hard segments and between 80 and 20 percent by weight of amorphous or relatively amorphous segments (soft segments), most preferably between 30 and 70 percent by weight of crystal segments or relatively hard and between 70 and 30 percent by weight of amorphous or relatively amorphous segments (soft segments). In soft segments, the molar percentage of comonomer can range between 10 and 90 mole percent, preferably between 20 and 80 mole percent, and most preferably between 33 and 75 mole percent. In the case where the comonomer is ethylene, it is preferably present in an amount between 10% mol and 90% mol, more preferably between 20% mol and 80% mol, and most preferably between 33% mol and 75% mol. Preferably, the copolymers comprise hard segments having between 90% mol and 100% mol of propylene. The hard segments may have more than 90% mol, preferably more than 93% mol and more preferably more than 95% mol of propylene, and most preferably more than 98% mol of propylene. Such hard segments have corresponding melting points that are 80 ° C and above, preferably 100 ° C and above, more preferably 115 ° C and above, and most preferably 120 ° C and above.

In some embodiments, the block copolymer composite materials of the invention have a Block Composite Index (BCI), as defined below, which is greater than zero, but less than about 0.4, or between about 0.1 and about 0.3. In other embodiments, the BCI is greater than about 0.4 and up to about 1.0. Additionally, the BCI may be in the range of between about 0.4 and about 0.7, between about 0.5 and about 0.7, or between about 0.6 and about 0.9. In some embodiments, the BCI is in the range of between about 0.3 and about 0.9, between about 0.3 and about 0.8, or between about 0.3 and about 0.7, between about 0.3 and about 0.6, between about 0.3 and about 0.5, or between about 0.3 and about 0.4. In other embodiments, the BCI is in the range of between about 0.4 and about 1.0, between about 0.5 and about 1.0, or between about 0.6 and about 1.0, between about 0.7 and about 1.0, between about 0.8 and about 1.0, or between about 0.9 and about 1.0.

The block composite materials preferably have a Tf greater than 100 ° C, preferably greater than 120 ° C, and more preferably greater than 125 ° C. Preferably, the MFR of the block composite material is between 0.1 and 1000 dg / min, more preferably between 0.1 and 50 dg / min, and more preferably between 0.1 and 30 dg / min.

Additionally, the block composites of this embodiment of the invention have a weight average molecular weight (Mw) between 10,000 and approximately 2,500,000, preferably between 35,000 and approximately 1,000,000 and more preferably between 50,000 and approximately 300,000 , preferably between 50,000 and about 200,000.

Preferably, the block composite polymers of the invention comprise ethylene, propylene, 1-butene or 4-methyl-1-pentene and optionally one or more comonomers in polymerized form. Preferably, the block copolymers of the crystalline block composites comprise in a polymerized form ethylene, propylene, 1-butene or 4-methyl-1-pentene and optionally one or more C ^4-20 α-olefin comonomers. Additional suitable comonomers are selected from diolefins, cyclic olefins and cyclic diolefins, halogenated vinyl compounds, and aromatic vinylidene compounds.

The comonomer content of the resulting block composite polymers can be measured using any suitable technique, with techniques based on nuclear magnetic resonance spectroscopy (NMR) being preferred.

Preferably, the crystalline block composite polymers of the invention comprise between 0.5 and 95% w / w of CEP, between 0.5 and 95% w / w of CAOP and between 5 and 99% w / w of copolymer block More preferably, the crystalline block composite polymers comprise between 0.5 and 79% w / w of CEP, between 0.5 and 79% w / w of CAOP and between 20 and 99% w / w of block copolymer , and more preferably between 0.5 and 49% w / w of CEP, between 0.5 and 49% w / w of CAOp and between 50 and 99% w / w of block copolymer. The percentages by weight are based on the total weight of crystalline block composite material. The sum of the percentages by weight of CEP, CAOP and block copolymer is equal to 100%.

Preferably, the block copolymers of the invention comprise between 5 and 95 percent by weight of crystalline ethylene blocks (CEB) and between 95 and 5 percent w / w of crystalline alpha-olefin blocks (CAOB). They can comprise between 10% w / w and 90% w / w CEB and between 90% w / w and 10% w / w CAOB. More preferably, the block copolymers comprise between 25 and 75% w / w of CEB and between 75 and 25% w / w of CAOB, and even more preferably comprise between 30 and 70% w / w of CEB and between 70 and 30 % p / p of CAOB.

In some embodiments, the block composite materials of the invention have a Crystal Block Composite Material Index (CBCI), as defined below, which is greater than zero, but less than about 0.4 or between about 0.1 and about 0.3. In other embodiments, the CBCI is greater than about 0.4 and up to about 1.0. In some embodiments, the CBCI is in the range between about 0.1 and about 0.9, between about 0.1 and about 0.8, between about 0.1 and about 0.7 or between about 0.1 and about 0.6. Additionally, the CBCI may be in the range of between about 0.4 and about 0.7, between about 0.5 and about 0.7, or between about 0.6 and about 0.9. In some embodiments, the CBCI is in the range between about 0.3 and about 0.9, between about 0.3 and about 0.8, or between about 0.3 and about 0.7, between about 0.3 and about 0.6, between about 0.3 and about 0.5, or between about 0.3 and about 0.4. In other embodiments, the CBCI is in the range of between about 0.4 and about 1.0, between about 0.5 and about 1.0, or between about 0.6 and about 1.0, between about 0.7 and about 1.0, between about 0.8 and about 1.0, or between about 0.9 and about 1.0.

Additionally, the crystalline block composite materials of this embodiment of the invention have a weight average molecular weight (Mw) between 1,000 and about 2,500,000, preferably between 35,000 and about 1,000,000 and more preferably between 50,000 and 500,000 , between 50,000 and approximately 300,000, and preferably between 50,000 and approximately 200,000.

The overall composition of each resin is determined by DSC, NMR, GPC, DMS and TEM morphology. Xylene fractionation and HTLC fractionation can also be used to estimate the performance of block copolymer, and in particular the index of block composite material. These are described in more detail in US Patent Application Publications. No. US2011-0082257, US2011-0082258 and US2011-0082249.

Differential scanning calorimetry (DSC) is used to measure, among other things, the melting heats of crystalline blocks and block composite materials, and is carried out on a TA Instruments Q1000 DSC device equipped with an accessory RCS cooling and an automatic sampler. A nitrogen flow purge of 50 mL / min is used. The sample is compacted in a thin sheet and melted in the press at approximately 190 ° C and then cooled with air at room temperature (25 ° C). Then approximately 3-10 mg of material is cut, weighed accurately, and placed in a lightweight aluminum capsule (approx. 50 mg) which is then closed. The thermal behavior of the sample is investigated with the following temperature profile: the sample is rapidly heated to 190 ° C and maintained isothermal for 3 minutes in order to eliminate any previous thermal history. The sample is then cooled to -90 ° C with a cooling ramp of 10 ° C / min and maintained at -90 ° C for 3 minutes. The sample is then heated to 190 ° C with a heating ramp of 10 ° C / min. The cooling and second heating curves are recorded. For melting heat measurements corresponding to the specified CBC and BC resins, as is known and routinely carried out by specialists in this area, the baseline is drawn for the calculation from the initial flat section prior to the start of the fusion (typically in the range of between about -10 ° C and about -20 ° C for these types of materials) and extends until the end of the melting of the second heating curve.

In summary:

Suitable composite block (BC's) resins comprise:

i) An ethylene polymer (EP) comprising between about 80 and about 90 mol% of polymerized ethylene, preferably at least about 85 mol%;

ii) An alpha-olefin based crystalline polymer (CAOP); Y

iii) A block copolymer comprising (a) a block of ethylene polymer (EB) comprising between about 80 and about 90% mol of ethylene and (b) a crystalline block of alpha-olefin (CAOB).

Crystalline block composite resins (CBC's) comprise:

i) A crystalline ethylene polymer (CEP) comprising at least more than about 90% mol of polymerized ethylene, preferably at least about 93% mol;

ii) An alpha-olefin based crystalline polymer (CAOP); Y

iii) A block copolymer comprising (a) a block of crystalline ethylene polymer (CEB) comprising at least more than about 90 mol% of polymerized ethylene, preferably at least about 93 mol% and (b) a block of crystalline alpha-olefin (CAOB).

Another way of collectively summarizing the suitable resin (s) used in Layer B is that it comprises a CBC or a specified BC comprising:

i) An ethylene polymer comprising at least about 80% mol of polymerized ethylene, preferably at least about 85% mol, more preferably at least about 90% mol, and most preferably at least about 93% mol of polymerized ethylene;

ii) An alpha-olefin based crystalline polymer (CAOP); Y

iii) A block copolymer comprising (a) an ethylene polymer block comprising at least about 80 mol% of polymerized ethylene, preferably at least about 85 mol%, more preferably at least about 90 mol%, and most preferably at least about 93 mol% of polymerized ethylene and (b) a block of crystalline alpha-olefin (CAOB).

The suitable BC and / or CBC resin (s) suitable for Layer B (s) has an amount of CAOB (in part (iii)) in the range of between approximately 30 and approximately 70% by weight (based on (iii)), preferably at least about 40% w / w, more preferably at least about 45% w / w and most preferably about 50% w / w, and preferably up to about 60% w / w / p, and preferably up to about 55% w / w (the balance in each case is ethylene polymer). It has also been observed that the suitable BC and / or CBC resin (s) for Layer B has an index of block (crystalline) composite material of at least about 0.1, preferably at least about 0.3, preferably at least about 0.5 and more preferably at least about 0.7. Another way of characterizing the suitable BC and / or CBC resin (s) essential for layer B is to have an MFR in the range between about 1 and about 50 dg / min; preferably at least about 2, more preferably at least about 3; and preferably up to about 40, and preferably up to about 30 g / min.

In general, BCs that can be used in Layer B according to the present invention will have heat fusion values (generally related to their ethylene content in e P and EB) of at least about 75 joules per gram (J / g ), more preferably of at least about 80 J / g, even more preferably of at least about 85 J / g and most preferably of at least about 90 J / g, measured by DSC. In general, the CBC's that can be used in Layer B according to the present invention will have heat fusion values (reflecting the relatively higher ethylene content in the CEP and the CEB) measured by DSC of at least about 85 joules per gram ( J / g), more preferably at least about 90 J / g. In any case, the heat fusion values for polymers of these types would generally have a maximum in the area of approximately 125 J / g. For heat fusion measurements, as is generally known and practiced by specialists in this area, the DSC is applied as described generally below, with nitrogen at 10 ° C / min from 23 ° C up to 220 ° C, keeping isothermal at 220 ° C, go down to 23 ° C at 10 ° C / min and return to 220 ° C at 10 ° C / min. The second heat data is used to calculate the heat of fusion of the melting transition.

Mixtures of these resins may also be used when mixed or diluted with one or more additional polymers, including polyolefins such as those described herein, to the point where (i) the additional polymer is miscible or highly compatible with BC and / or the CBC, (ii) the additional polymer has little or no negative impact on the desirable properties of the polyolefin block copolymer composite material, e.g., hardness and modulus, and (iii) the (s) ) BC and / or CBC resin (s) constitutes (n) between at least about 40 and 99 percent by weight of the mixture, preferably at least about 60, more preferably at least about 75, and more preferably at least about 75 , and more preferably at least about 80 percent by weight of the mixture. The mixture can be used to provide: improved compatibility (adhesion) with C and / or other layers in a range of lower cost conditions. In particular, the mixtures would be desirably employed when Layer B is used as a surface layer, as discussed below, and said film surface needs sufficient properties to roll, handle, package, transport and mount on the final laminated structures. , such as in electronic device modules.

Layer A of the backsheet

Layer A according to the present invention, often referred to as a "sealing" layer, is selected to be adhered, preferably by co-extrusion or alternatively, but less preferably, by a lamination process (such as extrusion lamination, thermal lamination or adhesive lamination) to the tie layer (Layer B) in production of the film according to the invention and to adhere the film to other films or articles such as encapsulation films used in the assembly of electronic devices ("encapsulation films" which are discussed as more detail below). Layer A materials can be selected from a wide variety of different types of materials used in mixtures and / or layers as described in more detail. ahead. Among other things, the relative thinness of Layer A distinguishes it from a layer that would serve as the "encapsulation" layer.

The wide variety of candidate materials for the sealing layer generally includes a wide range of ethylene-based thermoplastic polymers, such as radical-free and high-pressure low density polyethylene (LDPE), ethylene-based polymers prepared with Ziegler catalysts. Natta, which include heterogeneous high density polyethylene (HDPE) and heterogeneous linear low density polyethylene (LLDPE), ultra low density polyethylene (ULDPE), and very low density polyethylene (VLDPE), as well as multiple reactor ethylene polymers (mixtures "In-reactor" of Ziegler-Natta PE and metallocene PE, such as the products described in US Pat. Nos. 6,545,088 (Kolthammer et al.); 6,538,070 (Cardwell et al.) ; 6,566,446 (Parikh et al.); 5,844,045 (Kolthammer et al.); 5,869,575 (Kolthammer et al.); And 6,448,341 (Kolthammer et al.)). Commercial examples of linear ethylene-based polymers include the ATTANE ™ ultra low density linear polyethylene copolymer, DOWLEX ™ polyethylene resins, and FLEXOMER ™ very low density polyethylene, all available from The Dow Chemical Company. Other suitable synthetic polymers include ethylene / diene interpolymers, ethylene-acrylic acid (EAA), ethylene vinyl acetate (EVA), ethylene-ethyl acrylate (EEA), ethylene-methyl acrylate (EMA), ethylene-n-butyl acrylate (EnBA) , ethylene-methacrylic acid (EMAA), various types of ionomers, and ethylene / vinyl alcohol copolymers. Homogeneous olefin-based polymers such as ethylene-based plastomers or elastomers may also be useful as components of the mixtures or compounds prepared with the ethylenic polymers of this invention. Commercial examples of homogeneous ethylene-based plastomers or elastomers, catalyzed by metallocenes, include AFFINITY ™ polyolefin plastomers and ENGAGE ™ polyolefin elastomers, both available from The Dow Chemical Company, and commercial examples of plastomers and elastomers based on homogeneous propylene includes VERSFY ™ high performance polymers, available from The Dow Chemical Company, and VISTAMAX ™ polymers available from ExxonMobil Chemical Company.

Layer A olefinic interpolymers

Some specific preferred examples of olefinic interpolymers useful in this invention, particularly in the upper layer of the backsheet, include very low density polyethylene (VLDPE) (eg, FLEXOMER ™ ethylene / 1-hexene polyethylene manufactured by The Dow Chemical Company), homogeneously branched ethylene / a-olefin copolymers, linear (eg, TAFMER ™ from Mitsui Petrochemicals Company Limited and EXACT ™ from Exxon Chemical Company), homogeneously branched ethylene / a-olefin polymers, substantially linear (p eg, polyethylene AFFINITY ™ and ENGAGE ™ available from The Dow Chemical Company), and multi-block ethylene copolymers (eg, INFUSE ™ olefin block copolymers available from The Dow Chemical Company). The most preferred polyolefin copolymers for use in the upper layer of the backsheet are homogeneously linear and substantially linear branched ethylene copolymers, particularly the substantially linear ethylene copolymers described in more detail in US Pat. 5,272,236, 5,278,272 and 5,986,028 and the multi-block ethylene copolymers described in more detail in USP 7.355.089, WO 2005/090427, US2006 / 0199931, US2006 / 0199930, US2006 / 0199914, US2006 / 0199912, US2006 / 0199911, US2006 / 0199910, US2006 / 0199908, US2006 / 0199906, US2006 / 0199905, US2006 / 0199897, US2006 / 0199896, US2006 / 0199887, US2006 / 0199884, US2006 / 019919098/0199190989/0199190989/0199190989/0199190990/01991902 , US2006 / 0199006 and US2006 / 0199983.

Layer A polar ethylene copolymers

A preferred polar ethylene copolymer for use in the top layer of the claimed films is an EVA copolymer, which includes mixtures comprising eVa copolymers, which will form a sealing relationship with other films or layers, e.g., encapsulant, a sheet of cover glass, etc., when they contact adhesive with the layer or other component. The ratio of units derived from ethylene to units derived from vinyl acetate in the copolymer, before anchoring or other modification, can vary widely, but typically the EVA copolymer contains at least about 1, preferably at least about 2, more preferably at least about 4 and even more preferably at least about 6% w / w units derived from vinyl acetate. Typically, the EVA copolymer contains less than about 33% w / w units derived from vinyl acetate, preferably less than about 30, preferably less than about 25, preferably less than about 22, preferably less than about 18, and more preferably less than about 15% w / w units derived from vinyl acetate. The EVA copolymer can be prepared by any process that includes emulsion, dissolution and high-pressure polymerization.

The EVA copolymer before anchoring or other modification typically has a density of less than about 0.95, preferably less than about 0.945, more preferably less than about 0.94 g / cm 3. The same EVA copolymer typically has a density greater than about 0.9, preferably greater than 0.92 and more preferably greater than about 0.925 g / cm 3. Density is measured by the procedure of ASTM D-792. EVA copolymers are generally characterized as semi-crystalline, flexible and with good optical properties, eg, high visible and UV light transmission and low turbidity.

Another preferred polar ethylene copolymer useful as a top layer of the backsheet is an ethylene acrylate copolymer such as ethylene ethyl acrylate (EEA) and ethylene methyl acrylate (EMA) copolymers (including mixtures comprising any of them), which they can also form a sealing relationship with the adjacent layer, such as an encapsulating layer in an electronic device module, when put in adhesive contact. The ratio of units derived from ethylene to units derived from ethyl acrylate or methyl acrylate in the copolymer, before anchoring or other modification, can vary widely, but typically the EEA or EMA copolymer contains at least about 1, preferably at least about 2, more preferably at least about 4 and even more preferably at least about 6,% w / w units derived from ethyl acrylate or methyl acrylate. Typically, the EEA or EMA copolymer contains less than about 28, preferably less than about 25, more preferably less than 22, and more preferably less than about 19,% w / w units derived from ethyl acrylate or methyl acrylate.

These polar ethylene copolymers (eg, EVA, EEA or EMA copolymers) typically have a melt index (MI, as measured by the procedure of ASTM D-1238 (190C / 2.16kg) under 100, preferably less than 75, more preferably less than 50 and even more preferably less than 30, g / 10min The typical minimum MI is at least about 0.3, more preferably 0.7, and more preferably is at least about 1 g / 10 minutes.

A preferred top layer of the backsheet is a blend formulation of a linear low density polyethylene (LLDPE) comprising polar ethylene copolymer in an amount of between about 10 and about 45% by weight, depending on the weight% of the copolymer. of polar ethylene that is being used.

MAH-m-Polyolefins of Layer A

MAH-m-polyolefins are another preferred sealing layer material and include MAH-g-polyolefins and MAH interpolymers, that is, MAH functionality is present in the polyolefin by anchoring on the polymer main chain or incorporating functionality into the main chain through copolymerization of MAH with the olefin monomer.

In one embodiment of the invention, the polyolefin is modified by anchoring to enhance the interlayer adhesion between the upper layer and the lower layer of the multilayer structure, through a reaction of the functionality anchored with the reactive group present in the mooring layer. intermediate. As anchoring material, any material that can be anchored to the polyolefin and which can react with the reactive group present in the tie layer can be used.

As the anchoring material, any unsaturated organic compound containing at least one ethylenic unsaturation (eg, at least one double bond), at least one carbonyl group (-C = O), and which is anchored to the polymer of polyolefin and more particularly to EVA, EEA, EMA or polypropylene. Representative examples of compounds containing at least one carbonyl group are carboxylic acids, anhydrides, esters and their salts, both metallic and nonmetallic. Preferably, the organic compound contains an ethylenic unsaturation conjugated with a carbonyl group. Representative compounds include maleic, fumaric, acrylic, methacrylic, itaconic, crotonic, a-methyl crotonic and cinnamic acid and their anhydride, ester and salt derivatives, if any. Maleic anhydride is the preferred unsaturated organic compound that contains at least one ethylenic unsaturation and at least one carbonyl group.

The unsaturated organic compound content of the anchor polyolefin is at least about 0.01% w / w, and preferably at least about 0.05% w / w, based on the combined weight of the polyolefin and the organic compound. The maximum amount of unsaturated organic compound content may vary at convenience, but typically does not exceed approximately 10% w / w, preferably does not exceed approximately 5% w / w, and more preferably does not exceed approximately 2% w / w. This unsaturated content of the anchor polyolefin is measured by a titration method, eg, an anchor polyolefin / xylene solution with a potassium hydroxide solution (KOH) is titrated. MAH functionality may be present in the polyolefin, eg, by anchoring, or even by copolymerization with the olefin monomer.

The unsaturated organic compound can be anchored to the polyolefin by any known technique, such as those included in US Pat. 3,236,917 and 5,194,509. For example, in patent 3,236,917 the polymer is introduced into a double roller mixer and mixed at a temperature of 60 ° C. The unsaturated organic compound is then added together with a free radical initiator, such as, for example, benzoyl peroxide, and the components are mixed at 30 ° C until the anchor is complete. In patent 5,194,509, the process is similar except that the reaction temperature is higher, eg, from 210 to 300 ° C, and a free radical initiator is not used, or is used at a reduced concentration.

An alternative and preferred method of anchoring is shown in US Pat. 4,950,541 using a twin screw devolatilizer extruder as a mixing apparatus. The polymer and the unsaturated organic compound are mixed and reacted within the extruder at temperatures at which the reagents melt and in the presence of a free radical initiator. Preferably, the unsaturated organic compound is injected into a pressure maintained area within the extruder.

Ethylene-based polymers with Layer A anchored silane

In another preferred embodiment, a material suitable for Layer A can be provided through a silane anchor polyolefin as described below for use as an encapsulation layer, particularly as provided by silane anchoring in thermoplastic polymers based on ethylene described above, which include an olefinic interpolymer or a polar ethylene copolymer described above. If used as Layer A in a backsheet film according to the present invention, as described below, the thickness of the silane anchor polyolefin layer would generally be less than about 200 microns (| jm), and more preferably less than 100 jm and not enough to act as the typical encapsulation layer that is usually a film with a thickness of approximately 450 jm. However, in layer A of the present films, it will provide a good seal using said materials in the encapsulation films.

Layer A crystalline olefin block composite material

In another preferred embodiment of the present invention and depending on the nature of the encapsulating film layer, a suitable sealant layer can be provided by a crystalline block copolymer composite material as described above. In a backsheet according to the present invention, depending on the specific selection of this type of crystalline block copolymer composite as layer B, layer B can act as both Layers, B and A. In a preferred embodiment, the present invention it is a new film comprising Layers B and C. In such an embodiment, it may also be desirable to incorporate a smaller amount (eg, less than 25%) of a polar ethylene copolymer in said crystalline block copolymer composite material .

Mixes

Mixtures comprising these polyolefin resins with others described above can also be used in Layer A of films according to the invention. In other words, Layer A polyolefin polymers can be mixed or diluted with one or more additional polymers to the point where the polyolefin is (i) miscible with the other polymer, (ii) the other polymer has little, or none, negative impact on the desirable properties of the polyolefin polymer, eg, hardness and modulus, and (iii) the polyolefin polymer of this invention constitutes at least about 55, preferably at least about 70, preferably at least about 75 and more preferably at least about 80 percent by weight of the mixture.

Cross-linking in Layers A or B

Although crosslinking will preferably be avoided, due to the low density and modulus of polyolefin resins used in the practical application of this invention, these polymers can be cured or crosslinked at the time of lamination or after, usually shortly after, assembly. of the layers in the multilayer article, eg, the PV module. Crosslinking can be initiated and carried out by any one of a number of different and known methods, eg, by the use of thermally activated initiators, eg, peroxides and azo compounds; photoinitiators, eg benzophenone; radiation techniques that include electron rays and X-rays; vinyl silane, eg, vinyl tri-ethoxy or vinyl trimethoxy silane; and moisture cure.

The stabilized polypropylene layer of the backsheet of the PV module of this invention exhibits (1) a low flame spread of <100 measured by ASTM E162-02a, (2) long-term thermal aging greater than 10 ° C measured through the Relative Thermal Index (RTI) and evaluated by UL 746B and reflected in the retention of tensile strength measured through ASTM D882 after aging at high temperatures (e.g., 150 ° C) , and (3) UV stability greater than (>) 1000 hours, reflected through a retention of> 70% of tensile strength properties and good color retention (eg, YI less than (<5) 5) in exposure to xenon arc (IEC 61730, ASTM D2565, ASTM G151, ASTM G155) or alternatively in QUV exposure (ASTM G154). Additionally, the PV back sheets and the integrated back sheets with stabilized polypropylene layer also exhibit a low flame propagation index of <100 and good resistance to environmental conditions and a good long-term thermal aging property.

In the stabilized polypropylene layer of the PV module backsheet, the total amount of HALS typically ranges from 0.5 to 3.0 percent by weight (% w / w), the total amount of hindered hydroxybenzoate is typically between 0 and 1.5% w / w, the total amount of ortho-hydroxy triazine in the back sheet of the PV module is typically between 0 and 0.3% w / w), the total amount of thioester is typically between 0.1 and 0.8%

Stabilizers

Ortho-hydroxy triazine compound

The ortho-hydroxy triazine compounds that can be used in the practical application of this invention are known compounds and are described in US Pat. 6,843,939. A representative example of the orthohydroxy triazine compounds that can be used in the practical application of this invention is CYASORB ™ UV-1164 (2,4-bis (2,4-dimethylphenyl) -6- (2-hydroxy-4-isooctyloxyphenyl) ) -1,3,5-triazine (CAS 2725-22-6)). The amount of ortho-hydroxy triazine compound used in the polypropylene layer is typically 50 to 10,000 parts per million (ppm), more typically greater (>) 75 to 8,000 ppm, more typically 100 to 6,000 ppm, and even more typically 100 to 4,000 ppm.

Obstructed Amine Light Stabilizer ( HALS)

The HALS that can be used in the practical application of this invention are also known compounds and contain at least one 2,2,6,6-tetraalkylpiperidine (HALS-1) or 2,2,6,6-tetraalkylpiperazinone (HALS-2) radical ). These HALS are also described in U.S. Pat. 6,843,939, and can be used alone or in combination with each other. If used in combination with each other, the weight ratio of one to the other can vary widely, eg, HALS-1: HALS-2 from 1:99 to 99: 1, from 5: 1 to 1: 5, from 4: 1 to 1: 4, from 3: 1 to 1: 3, from 2: 1 to 1: 2 and 1: 1. Typically and preferably the HALS used in the practical application of this invention are oligomeric or polymeric or have a weight average molecular weight (Mw) of at least 500 grams per mole (g / mol), more typically at least 1,000 g / mol or even more typically of at least 1,500 g / mol.

HALS that can be used in the practical application of this invention include, but are not limited to, and available from Cytec, the following: CYASORB ™ UV 3346 (1,6-hexanediamine, -N, N'-bis (2,2,6 , 6-tetramethyl-4-piperidinyl) (CAS No. 82451-48-7) polymers with 2,4-dichloro-6- (4-morpholinyl) -1,3,5-triazine, from Cyasorb); CYASORB ™ 3529 (CAS No. 193098 40-7) 1,6-hexanediamine-N, N'-bis (2,2,6,6-tetramethyl-4-piperidinyl) polymers with morpholine reaction products-2.4.6 - trichloro-1,3,5, methylated triazine; CYASORB ™ UV 3853 (CAS No. 167078-06-0) 2,2,6,6-tetramethyl-4-piperidinyl stearate; CYASORB ™ THT 4611 (CAS No. 82451-48-7) 1,6-hexanediamine-N, N'-bis (2,2,6,6-tetramethyl-4-piperidinyl) polymers with 2,4-dichloro-6 - (4-morpholinyl) -1,3,5-triazine and 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy) phenol ) (CAS No. 2725-22-6); CYASORB ™ THT 6435 (CAS No. 193098-40-7) 1,6-hexanediamine-N, N'-bis (2,2,6,6-tetramethyl-4-piperidinyl) polymers with morpholine-2 reaction products , 4,6-trichloro-1,3,5-triazine, methylated and 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy ) phenol) (CAS No. 2725-22-6); CYASORB CYNERGY SOLUTIONS ™ R350-a4 (a mixture of stabilizers comprising CYASORB ™ UV-3529, CYASORB ™ 1164 (an ortho-hydroxy triazine), and DOVERPHOS ™ 9228 (a phosphite)); CYASORB ™ R350 (a mixture of stabilizers comprising CYASOr B ™ UV-3346, CYASORB ™ UV-3529, CYASORB ™ UV-2908 (a hindered hydroxybenzoate), CYASORB ™ UV-1164 and CYANOX ™ 1790); CYASORB ™ A400 (a mixture of stabilizers comprising CYASORB ™ UV-3529, CYASORB ™ UV-2908, and IRGAFOS ™ 168 (a phosphite)); CYASORB ™ A430 (a mixture of stabilizers comprising CYASORB ™ UV-3529, CYASORB ™ UV-2908, and IRGAFQS ™ 168); NOR 371 HALS (1,6-hexanediamine-N, N'-bis (2,2,6,6-tetramethyl-4-piperidinyl) polymer with 2,4,6-trichloro-1,3,5 reaction products -triazine with 3-bromo-1-propene, N-butyl-1-butanamine and N-butyl-2,2,6,6-tetramethyl-4-piperidinamine, oxidized, hydrogenated) available from BASF; NOR 116 HALS (reaction products of 1,3-propanediamine-N, N "-1,2-ethanediylbis with cyclohexane and reaction products of N-butyl-2,2,6,6-tetramethyl-4-piperidinamine-2 , 4,6-trichloro-1,3,5-triazine peroxide, CAS No. 191680-81-6) available from BASF; CHIMASSORB ™ 119 (1,5,8,12-tetrakis [4,6-bis (N -butyl-N-1.2.2.6.6- pentameti-4-piperidylamino) -1,3,5-triazin-2-yl] -1,5,8,12-tetraazadodecane (CAS No. 106990-43-6) available in BASF; CHIMASSORb ™ 966 and similar structures with low melting points (see US 2012/0108711), sterically hindered amine stabilizers with four hanging 2,2,6,6-tetramethyl-piperidine groups; and AZONOR bis ( 1-Propyloxy-2,2,6,6-tetramethylpiperidyl) -4-diazine (as described, for example, in US 2010/0144935) Mixtures of CYASORB ™ UV 3346 and 3529 are the preferred HALS.

In one embodiment, a mixture of CYASORB ™ UV 3346 and UV 3529 is used with a mass ratio of 1: 4 to 8: 1, more typically 1: 3 to 6: 1, even more typically 1: 2 to 5: 1 .

The amount of HALS used in the polypropylene layer is typically between 500 and 30,000 parts per million (ppm), more typically above (>) 2,000 to 20,000 ppm, more typically> 5,000 to 15,000 ppm, and even more typically between 7,500 and 12,000 ppm.

The weight ratio of HALS to ortho-hydroxy triazine is typically 20: 1 to 1: 2, more typically 10: 1 to 1: 1, more typically 8: 1 to 4: 1, and even more typically of 7: 1 to 5: 1.

Hydroxybenzoate hindered

The hindered hydroxybenzoate compounds that can be used in the practical application of this invention are also known compounds and are described in US Pat. 6,843,939. They include, but are not limited to, CYASORB ™ or V-2908 (hexadecyl ester of 3,5-di-tert-butyl-4-hydroxybenzoic acid (Ca sn ° 67845-93-6)), and CYASORB ™ UV-3853 (stearate of 2,2,6,6-tetramethyl-4-piperidinyl (CAS No. 167078-06-0)). CYASORB ™ UV-2908 is a preferred hindered hydroxybenzoate. The amount of hindered hydroxybenzoate compound used in the polypropylene layer is typically between 500 and 25,000 parts per million (ppm), more typically above (>) 2,000 to 20,000 ppm, more typically> 5,000 to 18,000 ppm, and even more typically 7,500 to 15,000 ppm.

The weight ratio of hindered hydroxybenzoate to HALS is typically between 1: 8 and 10: 1, more typically between 0.5: 1 and 8: 1, more typically between 0.75: 1 and 4: 1, and even more typically between 1: 1 and 2: 1.

Thioester

The thioesters that can be used in the practical application of this invention are also known compounds, and are secondary antioxidants containing sulfur and ester groups. [Gachter / Muller, Plastics Additives Handbook, Hanser Publishers, 1993] The thioesters that can be used in the practical application of this invention include, but are not limited to, NAUGARD ™ 412S (pentaerythritol tetrakis (p-laurylthiopropionate), CAS No. 29598-76-3, from Chemtura), LOWINOX ™ DSTDP (distearyl thiodipropionate, CAS No. 693-36-7 from Chemtura), dilauryl thiodipropionate, CAS No. 123-28-4, from Chemtura, and SN-1 (acid propanoic acid, 3- (dodecylthio) -1,1 '- [oxybis (2,1-ethanediyloxy-2,1-ethanediyl)] ester, CAS No. 64253-30-1, an antioxidant from Tiarco). NAUGARD ™ 412S is a preferred thioester for use in the practical application of this invention. The amount of thioester used in the polypropylene layer is typically 1,500 to 12,000 parts per million (ppm), more typically> 2,000 to 10,000 ppm, more typically> 2,500 to 8,000 ppm, and even more typically 3,000 to 6,000 ppm.

Flame retardants

In certain embodiments of this invention, one or more layers of the backsheet of the PV module comprises a flame retardant. Such flame retardants can be used alone or in combination with another flame retardant. The flame retardants used in the practical application of this invention can be confined to a single layer of the backsheet or spread along multiple layers, or all layers of the backsheet. Typically such flame retardants are present, if they are, in an aggregate amount, that is, the total of all flame retardants of the backsheet, between 0 and 50, more typically between 0 and 30 and even more typically between 0 and 10% w / w based on the weight of the backsheet.

Non-halogenated organic compound

Non-halogenated organic compounds that can be used in the practical application of this invention include, but are not limited to, melamine-containing compounds such as melamine cyanurate, melamine phosphate, melamine pyrophosphate, melamine polyphosphate, 2,4,6-triamino -1,3,5-triazine, and mixtures of piperazine pyrophosphate and melamine pyrophosphate and the like.

Halogenated non-phosphorous organic compound

Halogenated non-phosphorous organic compounds that can be used in the practical application of this invention include, but are not limited to, chlorinated paraffin, halogenated aromatic compounds such as pentabromotoluene, decabromodiphenyl oxide, decabromodiphenyl ethane, ethylene-bis (tetrabromophthalimide), declorane plus, and Similar.

Halogen phosphorous compounds

Non-limiting examples of suitable halogenated phosphates include the halogenated versions (fluoro-, chloro-, bromo- and / or iodo-) of triphenyl phosphate (TPP), resorcinol diphenyl phosphate (RDP), bisphenol A diphenyl phosphate, and (2, 6-dimethylphenyl) 1,3-phenylene bisphosphate.

Anti-drip agent

The anti-drip agent prevents the composition from dripping when exposed to flame. Non-limiting examples of suitable anti-drip agents include fluoro-resin, such as poly (tetrafluoroethylene), polyvinylidene fluoride or tetrafluoroethylene / hexafluoropropylene copolymers and ethylene / tetrafluoroethylene copolymers, styrene copolymer with TEFLON / T-acrylonitrile-acrylonitrile ), fluorinated polyolefin, lithium, sodium, potassium or cesium salt of 1,1,2,2-tetrafluoroethanesulfonate or 1,1,2,3,3,3-hexafluoropropanesulfonate. Other non-limiting examples of suitable anti-drip agents include silicone resins, silicone oil, clay, phosphoric acid, phosphorous acid, hypophosphorous acid, hypophosphoric acid, phosphonic acid, phosphonic acid, metaphosphoric acid, hexanophosphoric acid, thiophosphoric acid, fluorophosphoric acid, difluorophosphoric acid, fluorophosphorous acid, difluorophosphorous acid, fluorohypophosphorous acid and fluorohypophosphoric acid. The anti-drip agent can be one or more of any of the anti-drip agents mentioned above.

Additives

In one embodiment, the polypropylene layer further comprises at least one acid scavenger, a metal deactivator, a primary antioxidant (such as hindered phenol), and a secondary antioxidant (such as hindered arylalkyl phosphate or trisaryl phosphite). Representative phosphites include, but are not limited to, DOVERPHOS ™ 9228 (bis (2,4-dicumylphenyl) pentaerythritol disphosphite) available from Dover Chemical Company, and IRGAFOS ™ 168 phenol, 2,4-bis (1,1-dimethyl ethyl) -1 , 1 ', 1 "-phosphite (CAS No. 31570-04-4)). The amount of each additive used in the polypropylene layer is typically 100 to 4,000 parts per million (ppm), more typically 200 to 3,000 ppm, more typically 300 to 2,000 ppm, and even more typically 400 to 1,500 ppm.

The individual layers of the multilayer structure may further comprise one or more additives in addition to the stabilizing additives. Other additives that can be used include anti-blockages such as diatomaceous earths, superfloss, silicates, talcum, mica, wollastonite and epoxy coated talc, and the like; strip additives such as erucamide and stearamide and the like, polymer process additives such as Dyneon fluoropolymer elastomers such as DYNAMAR ™ FX5930, pigments and fillers such as TiO2 R960, R350, R105, R108, R104, carbon blacks such as used in the Dow DNFA-0037 master lot or provided by Cabot. These and other potential additives are used in the manner and in the amount commonly used in the art.

Multilayer film structures and ED modules

In describing the use of the above polymer components to manufacture laminated or layered structures, there are a number of terms that are used on a regular basis and that are defined as indicated below.

"Layer" means a coating or stratum of individual thickness that extends continuously or discontinuously or that covers a surface.

"Multi-layer" means at least two layers.

"Facial surface", "flat surface" and similar terms referring to films or layers mean the surfaces of the layers that are in contact with the opposite and adjacent surfaces of the adjacent layers. Facial surfaces differ from edge surfaces. A rectangular film or layer comprises two facial surfaces and four edge surfaces. A circular layer comprises two facial surfaces and a continuous edge surface.

"In adherent contact" and similar terms mean that a facial surface of one layer and a facial surface of another layer is in direct contact and bonding with respect to each other, such that one layer cannot be separated from the other. without damaging the facial surfaces in contact of both layers.

"Sealing ratio" and similar terms mean that two or more components, eg, two polymer layers, or one polymer layer and one electronic device, or one polymer layer and one glass cover sheet, etc. , join with each other in such a way, eg, by co-extrusion, lamination, coating, etc., that the interface formed by its union is separated from its immediate external environment.

"Backsheet", "photovoltaic backsheet", "PV sheet" and similar terms mean the coating on the back or back side of a PV module to protect the PV module during use and the environment. The backsheet is typically a plastic, which is in direct contact with the encapsulant of the back of the PV module, where the encapsulant of the back is typically in direct contact with the active elements such as crystalline silicone cells of the PV module. The backsheet can be monolayer or multilayer.

"Primary antioxidant" and similar terms mean free radical capture antioxidants that inhibit oxidation via chain termination reactions. Typically, they have reactive OH or NH groups such as hindered phenols and secondary aromatic amines. Inhibition occurs by transferring a proton to the free radical species. The resulting radical is stable and does not abstract a proton from the polymer chain. An example of a primary antioxidant is Irganox 1076 available from BASF.

"Secondary antioxidant" and similar terms mean hydroperoxide decomposers that break down hydroperoxides into non-radical, non-reactive and thermally stable products. They are often used in combination with primary antioxidants to give rise to synergistic stabilization effects and are usually organic molecules such as organophosphorus and sulfur-based compounds. An example of a secondary antioxidant is IRGAFOS ™ 168 available from BASF.

The polymeric materials discussed above can be used in this invention to construct a film or sheet of multilayer structure, which in turn is used to construct electronic device modules in the same way and using the same amounts as described in the art, e.g. ., as shown in USP 6,586,271, US 2001/0045229 A1, WO 99/05206 and WO 99/04971. These materials are used to construct "skins" for the electronic device, that is, multilayer structures for application to one or both facial surfaces of the device, particularly the back surface of said devices, that is, the "back plates". Preferably said multilayer structures, eg, backsheets, are co-extruded, that is, all layers of the multilayer structures are extruded at the same time, such that the multilayer structure is formed.

Depending on the intended use, the multilayer film or sheet structures according to the present invention can be designed to meet certain performance requirements, such as in the area of physical property performance, including hardness, transparency, tensile strength, interlayer adhesion. , and heat resistance; of electrical properties such as insulation, dielectric breakdown, partial discharge and resistance; reflectance; and appearance.

Layer C - comprising high melting polyolefin resins

In general, Layer C of the multilayer backsheet structures according to the present invention is prepared from "Layer C high melting point polyolefin resins" as discussed above. In a preferred embodiment, it is preferably a highly crystalline homopolymer polypropylene resin. Depending on the specific performance requirements for the film and / or a modular structure in which it is intended to be used, the thickness of the Layer C is typically in the range of between about 100 pm and about 375 pm. In relation to the minimum thickness, Layer C is preferably at least about 125 pm, more preferably at least about 150 pm, more preferably at least about 160 pm and most preferably at least about 170 pm thick. In relation to the maximum thickness, the thickness of the Layer C can be up to about 350 pm, said value including, preferably about 300 pm, more preferably about 275 pm and most preferably about 250 pm.

Layer B - comprising polyolefin block copolymer composite resin

In general, Layer B of the multilayer backsheet film structures according to the various embodiments of the present invention is prepared from "layer B polyolefin block composite resins" as discussed above. In a preferred embodiment, it is preferably a resin of crystalline block copolymer composite material. Depending on the specific performance requirements for the film and / or a modular structure in which it is intended to be used, the thickness of Layer B is typically in the range of between about 1 pm and about 200 pm. With respect to the minimum thickness, Layer B has the thickness necessary to join the adjacent Layers A and C and preferably can be at least about 2 pm, preferably at least about 3 pm, preferably at least about 4 pm, more preferably at least about 10 pm, more preferably at least about 15 pm, more preferably at least about 20 pm and most preferably at least about 25 pm thick. With respect to the maximum thickness, the thickness and cost of Layer B are desirably minimized, but preferably it is up to about 150 pm, including, preferably about 100 pm, more preferably about 75 pm and most preferably up to about 50 pm thick, value included.

According to the embodiment of the electronic device of the present invention, wherein the film is a backsheet comprising Layer C and wherein Layer B behaves as a tie down layer and sealing layer A for lamination to the encapsulating film, Layer B would typically range in thickness between about 20 and about 250 micrometers ("pm"). In said films, Layer B has only the thickness necessary to adhere to Layer C and seal the backsheet to the adjacent encapsulation layer of the electronic device, preferably at least about 30 pm, preferably at least about 40 pm, and most preferably at least about 50 pm thick. With respect to the maximum thickness, the thickness and cost of Layer B are desirably minimized but may preferably be up to about 225 pm, including, preferably about 200 pm, more preferably about 175 pm, and most preferably up to approximately 150 pm, value included. With Layer B as a surface sealing layer it is preferably a mixture comprising the CBC and one or more additional components such as polymer process additives, colorants, and slip or anti-block additives.

As mentioned above, in an embodiment of a multilayer article of the present invention, the upper or sealing layer A adheres the films according to the present invention to an encapsulating film. Depending on the specific performance requirements of the film and / or a module structure in which its use is intended, the thickness of Layer A is typically in the range of between about 15 pm and about 200 pm. With respect to the minimum thickness, Layer A has only the thickness necessary to adhere the backsheet to the encapsulation film layer and should be at least about 17 pm, preferably at least about 20 pm, more preferably at least about 23 pm and most preferably at least about 25 pm thick. With respect to the maximum thickness, the thickness and cost of Layer A are desirably minimized, but may be up to about 175 pm, including, preferably about 150 pm, more preferably about 130 pm, and most preferably up to approximately 125 pm, value included.

Structure and film thickness

The composition of the layers can be selected and optimized following the guidelines discussed herein depending on the intended film structure and the use of the film structure. For example, for use in multilayer films of laminated structures of electronic device according to the present invention, the films can be used as a 2-layer backsheet or a 3-layer backsheet (comprising both a tie down layer and a top layer of sealed). The films according to the present invention are suitable for use, inter alia, as backsheet layers pass direct use in laminated electronic device structures, such as, for example, PV modules.

In all cases, the upper facial surface of the multilayer film structure exhibits good adhesion to the facial surfaces of the encapsulation layer material that encapsulates the device.

Depending to some extent on the specific structure and the specific process for using the film or sheet that are structured according to the present invention, said film structures can be prepared by any of a large number of known film production processes, including, but without limitation, extrusion or co-extrusion methods such as blown film, modified blown film, satin and molding, as well as sheet extrusion using a stack roller. There are many known techniques that can be used to provide multilayer films (even films that include micro layers), including for example those of USP 5,094,788; USP 5,094,793; WO / 2010/096608; WO 2008/008875; USP 3,565,985; USP 3,557,265; USP 3,884,606; USP 4,842,791 and USP 6,685,872. Layers A, B and C of the films according to the present invention are selected to be adhered together simultaneously preferably by co-extrusion, or alternatively, but less preferably, by a lamination process (such as extrusion lamination, thermal lamination, or adhesive lamination) in the films according to the invention. Alternatively, but less preferably, a sequential process can be employed to adhere pairs of layers together to the third layer and any optional layer.

The total thickness of the multilayer films and, in particular, of the backsheet structures, according to the present invention, before bonding to other layers such as encapsulating layers, electronic devices and / or anything else, is typically between about 50 | jm and approximately 825 | jm. Preferably to provide sufficient physical properties and performance, the film thickness is at least about 75 jim, and more preferably at least about 125 jim. To maintain a light weight and low cost, but retain the required electrical properties, the film thickness is preferably 775 mm or less, more preferably 575 mm or less. This includes any additional optional layers that make up, and are an integral part of, the multilayer structure comprising layers A, B and C.

Structures and terms of the PV module

In embodiments of the electronic device (and especially the PV module) of the present invention, the top layer or cover sheet 13 and the top encapsulating layer 12a generally need to have a good, typically excellent transparency, which means transmission rates above of 90, preferably above 95 and even more preferably above 97 percent, measured by UV-vis spectroscopy (which measures the absorbance in the wavelength range of approximately 250-1200 nanometers. An alternative measure of transparency it is the internal mist method of ASTM D-1003-00. If transparency is not a requirement for the operation of the electronic device, then the polymeric material may contain filler and / or opaque pigment.

The thicknesses of all layers of the electronic device module, described in more detail below, both in an absolute and relative context with respect to each other, are not critical to this invention, and as such may vary widely depending on the overall design and of the purpose of the module. Typical thicknesses for the protective or encapsulating layers 12a and 12b are in the range of about 0.125 to about 2 millimeters (mm), and for the cover sheet in the range of about 0.125 to about 1.25 mm. The thickness of the electronic device can also vary widely.

Light transmission encapsulation layer or component

These layers are sometimes referred to in various types of PV module structures as "encapsulation" films or layers or "protective" films or layers or "adhesive" films or layers. Provided they are sufficiently light transmitting, these layers can employ the same resin and resin compositions described above in relation to their use as Layer A for the backsheet embodiments of the present invention. Typically, these layers act by encapsulating and protecting the inner photovoltaic cell from moisture and other types of physical deterioration, and adhere it to other layers, such as a glass or other top sheet material and / or backsheet layer. Among the desirable qualities for these films are optical clarity, good physical and moisture resistance properties, moldability and low cost. Suitable polymer compositions and films include those used, and in the same manner and in the same amounts, as the light transmitting layers used in the laminated structures of known PV modules, eg, those described in USP documents 6,586,271, US 2001/0045229 A1, WO 99/05206 and WO 99/04971. These materials can be used as a "skin" light transmitter for the PV cell, that is, they can be applied to any face or surface of the device that is reactive to light.

Light transmitting cover sheet

The light transmitting cover sheet layers, sometimes referred to in the various types of PV module structures as "cover", "protective" and / or "top sheet" layers, may be one or more of the sheet materials Rigid or flexible known. Alternatively to glass, or in addition to glass, other known materials can be used for one or more of the layers with which the laminating films according to the present invention are used. Such materials include, for example, materials such as polycarbonate, acrylic polymers, a polyacrylate, a cyclic polyolefin such as ethylene norbornene, metallocene-catalyzed polystyrene, polyethylene terephthalate, polyethylene naphthalate, fluoropolymers such as ETFE (ethylene-tetrafluoroethylene (PV) of polyvinyl), FEP (fluoroethylene-propylene), ECTFE (ethylene-chlorotrifluoroethylene), PVDF (polyvinylidene fluoride), and many other types of plastic or polymeric materials, including laminates, mixtures or alloys of two or more such materials. The location of the particular layers and the need for light transmission and / or other specific physical properties will determine the specific material selections. As needed and possibly based on their composition, the down-conversion / light stabilization formulations discussed above in the transparent cover sheets can be employed. However, the inherent stability of some of these may not require light stabilization according to the present invention.

When used in certain embodiments of the present invention, the "glass" used as a light transmitting cover sheet refers to a solid and fragile light transmitting solid, such as that used for windows, many bottles, or glasses, which includes , but not limited to, soda-lime glass, borosilicate glass, sugar glass, isinglass glass (Moscow glass), or aluminum oxynitride. In the technical sense, glass is an inorganic fusion product that has been cooled to a rigid condition without crystallizing. Many glasses contain silica as their main component and glass former.

Pure silicon dioxide (SIO2) glass (the same chemical compound as quartz, or, in its polycrystalline form, sand) does not absorb UV light and is used for applications that require transparency in this region. Individual large natural crystals of quartz are pure silicon dioxide, and after grinding are used for special high quality glass. Synthetic amorphous silica, an almost 100% pure form of quartz, is the raw material for the most expensive special glasses.

The glass layer of the laminated structure is typically one of, without limitation, window glass, plate glass, silicate glass, sheet glass, float glass, colored glass, special glass which can, for example, include ingredients to control solar heating, glass coated with powdered metals such as silver, glass coated with antimony and tin oxide and / or indium tin oxide, E-glass glass, and SOLEXIA ™ glass (available from PPG Industries of Pittsburgh, PA).

PVlaminated module structures

The methods of manufacturing PV modules known in the art can be easily adapted to use the multilayer backsheet film structures according to the present invention. For example, multilayer backsheet film structures according to the present invention can be used in PV modules, and methods of manufacturing PV modules such as those included in USP 6,586,271, US 2001/0045229 A1, WO can be used. 99/05206 and WO 99/04971.

In general, in the lamination process to build a laminated PV module, at least the following layers are contacted:

A. A layer of light-receiving top sheet (eg, a glass layer) having a "outer" light-receiving facial surface and an "inner" facial surface;

B. A light-transmitting thermoplastic polymer film having at least one layer of light-transmitting thermoplastic polymers comprising light conversion / light stabilization formulations according to the present invention, which has a glass-facing face surface and a directed towards the light-reactive surface of the PV cell and encapsulating the cell surface, provided that said layer may be optional in some module structures in which the PV cell material can be deposited directly on the receiving layer of the cell. light (eg, glass);

C. A PV cell;

D. A second layer of encapsulating film; Y

E. A back layer comprising glass or other back layer substrate.

With the layers or layer sub-assemblies assembled at the desired locations, the assembly process typically requires a lamination stage with heating and compression in sufficient conditions to create the necessary adhesion between the layers and, if needed in some layers or materials , the initiation of its crosslinking. If desired, the layers may be placed in a vacuum laminator for 10 to 20 minutes at rolling temperatures in order to obtain a layer-to-layer adhesion and, if necessary, cross-linking of the polymeric material of the encapsulation element. In general, at the lower end, the rolling temperatures have to be at least about 130 ° C, preferably at least about 140 ° C and, at the upper end, less than or equal to about 170 ° C, preferably lower or equal to approximately 160 ° C.

The invention is further described by the following examples, in which all parts and percentages are expressed by weight, unless otherwise indicated.

Specific realizations

Experimental multilayer sample films (film layers indicated by letters, eg, A, B and C) are prepared using the thermoplastic resin materials reported in Tables 1 and 2. When indicated, flow rates are measured in melt (MFR) according to ASTM D1238 (230 ° C / 2.16kg) and are presented in grams per 10 minutes (g / 10 min), and melt index (MI) values are measured according to ASTM D1238 (190 ° C / 2.16 kg) and are presented in g / 10 min. Density is measured according to ASTM D792 and is given in grams per cubic centimeter (g / cm3). Polypropylene polyolefins all have at least one melting peak greater than 125 ° C and melting heat values greater than 60 J / g.

Table 1

Resins used in the Examples

The crystalline block copolymer composite materials (CBC's) shown below are prepared as described above and are presented in Table 2. They have the following general characteristics:

(1) An ethylene-based polymer (EP) that is crystalline (CEP);

(2) A crystalline polymer based on propylene (CPP), and

(3) A block copolymer comprising

(A) An ethylene polymer (EB) block that is a crystalline ethylene block (CEB) and

(B) A block of crystalline propylene polymer (CEB).

Also included in Table 2, CBC samples are further characterized by the following:

% w / w PP - Proportion by weight of propylene in the CBC, measured by separation by high temperature liquid chromatography (HTLC) as described above.

Mw - Average molecular weight by weight of the CBC in Kg / mol, determined by gel permeation chromatography (GPC) as described above.

Mw / Mn - Distribution of molecular weights of the CBC, determined by GPC as described above. % w / w of C2 in CBC - Weight percentage of ethylene in CBC, determined by nuclear magnetic resonance (NMR), the balance is propylene.

Tm (° C) Peak 1 (Peak 2) - Peak melting temperature, determined by the second heating curve of differential scanning calorimetry (DSC). Peak 1 refers to the merger of CPPB or CPP, while Peak 2 refers to the merger of CEB or CEP.

Tc (° C) - Peak crystallization temperature, determined by DSC cooling scan.

Melting heat (J / g) - CBC melting heat measured as described above.

% mol of C2 in CEB - Molar percentage of ethylene in the crystalline ethylene block component (3) (A) (and also the crystalline ethylene polymer component (1) of the CBC), the comonomer balance in both cases is propylene

% w / w CPPB in block copolymer - Weight percentage of crystalline propylene polymer in the block copolymer component (3).

CBCI - Index of crystalline block copolymer composite material that reflects the content of the block copolymer (iii) in the CBC composition.

Table 2

CBC resin used in the experimental film

As also indicated in Tables 3 and 4, other commercially available additives and stabilizers are used in the formulation.

Table 3

Master lots

Table 4

UV stabilizer master batch formulation

Films are prepared using the processing conditions indicated in Tables 5-8 on molding film / sheet lines using a standard type of feed block configuration with a 30.5 cm (cm) width (mini) die , 76.2 cm wide die (pilot) or 152 cm wide die (N1) to produce monolayer or three layer film.

Table 5

Manufacturing conditions for experimental monolayer molding films 1-6

Table 6

Manufacturing conditions for experimental multilayer molding films 11-13

Table 7

Manufacturing conditions for experimental monolayer molding film 14

Table 8

Manufacturing conditions for experimental multilayer molding films 16 and 17

The comparative examples are 4 and 10 (PROTEKT ™ HD PV backsheet consisting of a three layer film (PROTEKT ™ / PET / EVA) and obtained from Madico de Woburn, MA), and 5, 9 and 15 (FORMEX ™ GK10 acquired from ITW Formex as a 250 mm (mm) monolayer electrical insulating polypropylene film that acts as a standard PP film used in RTI UL746B, which has an excellent LTHA capability defined through an RTI score of 115 ° C and a UL-94 flammability score of VTM-0).

The tensile strength (ASTM D822) is evaluated in the machine direction (MD) of the samples. Strips of 250 mm x 250 mm film (2 samples) are cut and clamped to hang vertically in air ovens. Samples are evaluated using 4 repetitions on an Instron tensile strength tester at 50 mm / min with a 5 mm gap and line fasteners.

The accelerated weather resistance test is performed by exposing the polypropylene layer to a QUV chamber according to ASTM G154 with an A340 bulb, an irradiance of 0.68 W / m2 and no dark cycle, or carried out in a Xenon Arc according to ASTM D2565 without water spray, black panel temperature of 89 ° C, 0.55 W / m2 at 340 nm, relative humidity of 50%, a boron / boron filter configuration and constant light. After the samples have been tested, they are removed and their tensile strength or color properties (yellowing index) ASTM E313 are evaluated.

The evaluation of the dielectric strength ASTM D149 is carried out on samples of 125 mm x 125 mm that hang vertically aging in an air oven. Duplicates are made.

The flame propagation index is measured in INTERTEK according to ASTM E162-02a in samples with dimensions of 150 mm x 450 mm, 5 repetitions and with a heat source in the line of sight of the PP side of the films.

Table 9

Formulations in% w / w corresponding to Examples 1-5

Table 10

Property withholding with oven and QUV exposure versus time corresponding to Examples 1-5

Table 11

Formulations in % w / w corresponding to Examples 6-10

The stabilized PP monolayers of Example 2 and 3 have a long-term thermal stability and resistance to much better environmental conditions than Comparative Example 1. Their retention of the tensile strength property at 155C, 145C and 135C is much higher than that of Ex. 1. They also have excellent tensile strength and elongation retention, and low color, after more than 15,000 hours of QUV exposure. After 1000 hours of QUV exposure, the elongation retention of Ex. 1 falls to approximately 15 to 20%, and the YI increases to approximately 63.

Table 12

Property withholding with oven and QUV exposure versus time corresponding to Examples 6-10

Ex. 11 and 12 are PV backsheet and back encapsulating composite material that have a PP layer with UV 5 with CYASORB CYNERGY SOLUTIONS ™ R350. Ex. 13 and 14 are PV backsheet and back encapsulating composite material having a PP monolayer with UV 7 with CYASORB CYNERGY SOLUTIONS ™ R350-4a. These examples showed excellent resistance to environmental conditions. Tensile strength retention is above 80% and YI is excellent after 2000 hours of exposure to Xenon Arc.

Table 13

Formulations in % w / w corresponding to Examples 11-13

Table 14

Formulation in % w / w corresponding to Example 14

Table 15

Tensile strength retention with thermal aging corresponding to Examples 14 and 15

Table 16

Formulations in % w / w corresponding to Examples 16 and 17

Table 17

Retention of properties with exposure to xenon arc corresponding to Examples 16 and 17

Table 18

Evaluation of radiant panel corresponding to Examples 16 and 17

The flame spread index of the backsheet provided in Ex. 8, which has an added FR agent, shows a flame spread index similar to Ex. 7, which does not have any added FR agents. Ex. 10 to 15 show a flame propagation index of 100 or less, required by IEC for PV modules.

It is specifically intended that the present invention is not limited to the embodiments and illustrations contained herein, but includes modified forms of said embodiments, including portions of the embodiments and combinations of elements of different embodiments, as reflected in the scope of the following claims.

Claims (8)

1. A polyolefin PV backsheet comprising a layer of polypropylene stabilized with (A) at least one amine hindered with 2,2,6,6-tetraalkylpiperdine or 2,2,6,6-tetraalkylpierazinone, alone or in combination with a triazine moiety, (B) a thioester, and further comprising (C) at least one hindered hydroxybenzoate and / or (D) an ortho hydroxyl triazine compound. 2. The PV backsheet of claim 1 further comprising at least one additional layer comprising a polyolefin other than polypropylene. 3. The PV backsheet of claim 1 or 2, wherein the triazine moiety is oligomeric, polymeric or has a weight average molecular weight (Mw) of at least 500. 4. The PV backsheet of claim 3, wherein the polypropylene layer further comprises at least one acid scavenger, acid deactivator, primary antioxidant, and a secondary antioxidant. 5. The PV backsheet of claim 4, comprising two outer layers joined by a tie layer in which at least one of the two outer layers is the polypropylene layer and the tie layer comprises the same stabilizers as the layer Polypropylene 6. The PV backsheet of any of the previous claims, comprising (C) the at least one hindered hydroxybenzoate. 7. The PV backsheet of any of the previous claims, comprising (D) the hydroxyl triazine compound. 8. A PV module comprising the polyolefin PV backsheet of claim 1 or 2.